1882.] 97 [Abbott. 



an opportunity of examining the structure of the deposit, and 

 resulted in the determination of the fact, that there have occurred 

 breaks in the progress of the accumulations, indicated by" the 

 exposure of strata of sand, sometimes a foot or more in thickness, 

 this again, being overcapped by a fresh accumulation of large 

 boulders and the coarse material of which the deposit as a whole, 

 is composed. A rapid flow of water passing over fine sand would 

 necessarily have the effect of carrying most of it away, and leaving 

 only the coarse material beneath, upon which the gravel borne by 

 the flood would be laid down. Occasionally, it is evident, that 

 fragments of these layers of sand have escaped obliteration — not 

 only this, but have retained such objects as happened to be resting 

 upon them at the time of their burial beneath an additional mass 

 of transported material, especially here where the rapid current 

 met with the tide waters of the river, and the force of the flow 

 was materially checked, if not wholly obliterated. 



One such stratum of fine sand, averaging a foot in depth and 

 extending nearly three hundred yards along the exposure, I had 

 the good fortune to examine when exposed, and found lying upon 

 it, not only the typical palaeolithic implement which I here ex- 

 hibit, but these four chipped stones of less definite shape, but 

 which are unmistakably artificial. They are all of argillite. 



These, it appears to me were left by the ancient man of the 

 Delaware valley, upon this little sandy island as it then was, at a 

 time when there was a cessation or diminution for a while, of the 

 floods that were derived from the melting of the glaciers that 

 still lingered in the mountains of the upper valley of the river. 



Just as to-day, any object left upon the sandy islands of the 

 present river will surely be covered by the deposit of sand and 

 mud, which the freshets of the coming spring will bring from the 

 upper valley of the stream, so these five argillite implements were 

 left and covered by a subsequent gravel-bearing flood. These 

 objects, five in number, taken from an undisturbed section of the 

 gravel were over capped by a deposit nearly seven feet in thick- 

 ness, itself wholly undisturbed, and containing several boulders 

 of large size. 



This I consider one of the most important of my " finds," as I 

 have never heretofore discovered any specimens, in situ, except 



PROCEEDINGS, B. S. N. H. VOL. XXII. 1 APRIL, 1883. 



